Method for rejuvenating hydroprocessing catalysts

Abstract

A process for removing vanadium and nickel deactivants from contaminated hydrodesulfurization catalysts comprising Group VIB and/or VIII active components on refractory oxide supports comprising contacting said catalysts with an aqueous solution of (1) oxalic acid and (2) at least one inorganic component selected from the class consisting of nitric acid and water-soluble nitrate salts. The removal of vanadium and nickel contaminants from the surface of a deactivated catalyst by the process of the invention substantially rejuvenates the catalyst for hydrodesulfurization purposes, provided such removal is accomplished prior to burning off any coke that may also be present on said catalysts.

We claim: 
     
       1. A process for rejuvenating a hydrodesulfurization catalyst comprising at least one Group VIB and/or Group VIII active component supported on an inorganic refractory oxide, said catalyst being deactivated with coke and at least 5 wt. % of nickel plus vanadium deactivants, calculated as the metals, which process comprises, prior to coke burn-off, contacting at a temperature between about 30° and 100° F said catalyst with an aqueous solution comprising oxalic acid and at least one inorganic component selected from the class consisting of nitric acid, sodium nitrate, ammonium nitrate, potassium nitrate, calcium nitrate, magnesium nitrate, copper nitrate and aluminum nitrate, said solution containing at least 20 g/l of oxalic acid and between about 40 and 100 g/l of nitrate anion and said contacting being such that at least 25% of the nickel plus vanadium deactivants is removed and a substantial proportion of the hydrodesulfurization activity of the catalyst is restored. 
     
     
       2. A process as defined in claim 1 wherein said aqueous solution contains at least 20 g/l of oxalic acid and between 50 and 75 g/l of nitrate anion. 
     
     
       3. A process as defined in claim 2 wherein said solution contains aluminum nitrate. 
     
     
       4. A process as defined in claim 3 wherein said contacting is carried out for a time period of at least 2 hours and with at least 5 ml of aqueous solution per gram of catalyst contacted with said aqueous solution. 
     
     
       5. A process as defined in claim 2 wherein said contacting is carried out for a time period of at least 2 hours and with at least 5 ml of aqueous solution per gram of catalyst contacted with said aqueous solution. 
     
     
       6. A process as defined in claim 1 wherein at least 50% of the nickel plus vanadium deactivants is removed and the hydrodesulfurization activity of the rejuvenated catalyst is at least 70% of the hydrodesulfurization activity of the original catalyst. 
     
     
       7. A process as defined in claim 6 wherein said aqueous solution contains aluminum nitrate. 
     
     
       8. A process for rejuvenating a hydrodesulfurization catalyst comprising cobalt and molybdenum active components supported on an inorganic refractory oxide, said catalyst being deactivated with coke and at least 5 wt. % of nickel plus vanadium deactivants, calculated as the metals, which process comprises contacting, prior to coke burn-off and at a temperature in the range of 60°-80° F and for a time period between 10 and 100 hours, said catalyst with an aqueous solution containing oxalic acid in a concentration of at least 20 g/l and one or more inorganic components selected from the class consisting of nitric acid and aluminum nitrate in a concentration of between 50 and 75 g/l of nitrate anion so as to remove at least 50% of the nickel plus vanadium deactivants, thereby restoring a substantial proportion of the hydrodesulfurization activity of the catalyst. 
     
     
       9. A process as defined in claim 8 wherein said inorganic component is aluminum nitrate.